History says
In 1998, archaeologists found a well-preserved track leading to a Roman quarry near Swindon, England. The grooves in the road on the right side were observed to be much deeper than those on the left side, which would make sense given that carts would be driven without any load on the way to the quarry, but would return laden with stone. These grooves suggest that the Romans drove on the left, at least in this particular location.[5]
In fact, some (e.g. C. Northcote Parkinson) believe that ancient travellers on horseback generally rode on the left side of the road. As more people are right-handed, horsemen would thus be able to hold the reins with their left hands and keep their right hand free—to offer in friendship to passing riders or to defend themselves with swords, if necessary.[citation needed]
The first legal reference in Britain to an order for traffic to remain on the left occurred in 1756 with regard to London Bridge.[citation needed] The Highway Act 1773 contained a recommendation that horse traffic should remain on the left and this is enshrined in the Highway Act 1835.[19]
In the late 1700s, the shift from left to right that took place in countries such as the United States was based on teamsters' use of large freight wagons pulled by several pairs of horses. The wagons had no driver’s seat, so a postilion sat on the left rear horse and held his whip in his right hand. Seated on the left, the driver preferred that other wagons pass him on the left so that he could be sure to keep clear of the wheels of oncoming wagons. He did that by driving on the right side of the road.[citation needed]. Other countries, for example France, adopted driving on the right as a result of Napoleonic occupation/control.
Countries that became part of the British Empire adopted the British keep-left rule, although many have since changed. Canada, for example, where the maritime provinces and Vancouver (later to become British Columbia) drove on the left,[citation needed] eventually changed to the right in order to[citation needed] make border crossings to and from the United States easier. Nova Scotia switched to driving on the right on April 15, 1923.[citation needed]
History says
In 1998, archaeologists found a well-preserved track leading to a Roman quarry near Swindon, England. The grooves in the road on the right side were observed to be much deeper than those on the left side, which would make sense given that carts would be driven without any load on the way to the quarry, but would return laden with stone. These grooves suggest that the Romans drove on the left, at least in this particular location.[5]
In fact, some (e.g. C. Northcote Parkinson) believe that ancient travellers on horseback generally rode on the left side of the road. As more people are right-handed, horsemen would thus be able to hold the reins with their left hands and keep their right hand free—to offer in friendship to passing riders or to defend themselves with swords, if necessary.[citation needed]
The first legal reference in Britain to an order for traffic to remain on the left occurred in 1756 with regard to London Bridge.[citation needed] The Highway Act 1773 contained a recommendation that horse traffic should remain on the left and this is enshrined in the Highway Act 1835.[19]
In the late 1700s, the shift from left to right that took place in countries such as the United States was based on teamsters' use of large freight wagons pulled by several pairs of horses. The wagons had no driver’s seat, so a postilion sat on the left rear horse and held his whip in his right hand. Seated on the left, the driver preferred that other wagons pass him on the left so that he could be sure to keep clear of the wheels of oncoming wagons. He did that by driving on the right side of the road.[citation needed]. Other countries, for example France, adopted driving on the right as a result of Napoleonic occupation/control.
Countries that became part of the British Empire adopted the British keep-left rule, although many have since changed. Canada, for example, where the maritime provinces and Vancouver (later to become British Columbia) drove on the left,[citation needed] eventually changed to the right in order to[citation needed] make border crossings to and from the United States easier. Nova Scotia switched to driving on the right on April 15, 1923.[citation needed]
read the full info on http://en.wikipedia.org/wiki/Left_Hand_Drive